Screwhead



G. J. HOLT S CREWHEA D Filed Feb. 23, 1940 JW/ Kiwi [/2023 3 waz uyx g wPatented Oct. 7, 1941 UNITED scaawnaa a Grant 3'. Holt, Melrose, Mass.Application February 2a, 1940, Serial No. 320,256

2Claims.

This invention relates to a screw-head having a novel form andarrangement of tool-receiving "slots by which certain advantages areobtained over screw-heads heretoiore' made. The invention represents animprovement over the screwheads shown and described in Letters PatentNo.

2,180,633, granted to Clarence G. Holt on Novem ber 21, 1939.

slot or channel In having a bottom It spaced above the level of theannular shoulder i8 which J is beneath the marginal portion oi the head.The

- therein.

. It is an object of the invention to provide a screw-head, which isoperatively engageable by a special tool adapted to ilt into therecesses in the head, for rapid assembling of structures in which screwsare employed, and which is also operable by an ordinary screwdriver. Itis another object of the invention to provide a screwhead having maximummechanicalstrength consistent with the other advantages sought. It is afurther object of the invention to provide a screw-head which can bemanufactured by a process of cold-forging whereby recesses of accuratelyuniform dimensions are obtainable therein so that each screw-head willhave a frictional ilt on the blades of the special driving tool tosupport the screw on the end of the tool.

It is a still further object oi the invention to provide a. slightwedging fit between some portions of the slots and the blades of aspecial driving tool.

For a more complete understanding of the invention, reference may be hadto the following description of an embodiment thereof, and to thedrawing of which Figure 1 is a perspective view of a machine screwhaving a head embodying the invention.

Figure 2 is a section on the line 22 of Fi ure 1. i 1

Figure 3 is a section on the line 3-3 01 Figure 1.

Figure 4 is a top plan view of the screw-head shown in Figure l.

Figure 5 is a perspective viewof an oval screwhead.

Figure 6 is a perspective view of a flat screwhead.

Figure 7 is a perspective view of a fillister screw-head.

Figure B is a perspective view of a special driving tool adapted for usewith the screw-heads shown on the drawing.

The figures in the drawing show a machine screw HI having a head i2 01the round type with a. convex top. It is evident that the same head canbe used on a wood screw, bolt, or any other equivalent member adapted tobe rotated. The screw-head is provided witha diametrical slot ll,howeven is of sufiicient depth to provide adequate purchase for ascrewdriver inserted In addition to the diametrical slot 14 are a pairof radial slots 20 and 22, which, as indicated in Figure 4, are arrangedat right angles to the slot H and extend from the sides 01' the slot IIto the outer edge of the head I2. The bottoms of the slots 20 and 22slope downwardly and outwardly from the inner ends of the slots to theouter ends thereof. The two side walls of the slot H are nearly parallelto each other, but, as indicated in Figure 4, these side walls flareaway from each other very slightly from the midpoint of the slot towardthe ends thereof to provide a wedgingfit for blades 24 of a specialdriving tool 25 such as is shown in Figure 8. The side walls of each ofthe radial slots 20 and 22 are substantially parallel and are ofaccurate, predetermined width so as to receive with a snug fit blades ofthe driving tool 26. Ordinarily the snug fit of the blades 24 in theradial slots would be suflicient to support the screw frictionally on.

the end of the tool. However, to make the frictional grip more reliable,a very slight curve may be given to the side walls of the diametricalslot It so that the central portion of the slot is slightly narrowed. Asthe tool 25 is pushed against the screw-head, the outer portions 21 ofthe blades 24 first enter the outer portions of the slots 14, 20 and 22.As the tool seats against I the top of the screw-head, the innerportions 2B of two of the blades 24 enter into a. wedging engagementwith a slightly constricted central portion or the diametrical slot l4,thus ensuring an adequate frictional grip on the screw. This greatlyfacilitates the operation 01. driving the screws. In order to obtainaccurate reproduction of the dimensions of the slots or recesses in thescrew-head, .a cold-forging process may be used such as is well known inthe art.

The slots 20 and 22, being very shallow at their deepest point; detractbut little from the strength of the screw-head as a whole. The slot II,which is adapted to receive an ordinary screwdriver or two of the fourlugs on a special driving tool. is deeper than the other two slots butdoes not seriously weaken the screw-head since the bottom 01' this slotis considerably above the level of the annular shoulder 18, but there isno other slot of equal depth in the head.

The oval screw-head shown in Figure 5 has a convex top surface 30 and afrusto-conical shoulder 32. In the top surface is a transverse slot orrecess 34 having nearly parallel side walls flaring slightly toward theends of the slot, and a level bottom. The end walls 36 may be inclined.Extending radially at right angles to the slot 34 are a pair of recesses38. The side walls of these recesses are parallel and the bot-,

toms slope outwardly and downwardly to a point near the outer end ofeach recess. From that point the bottom slopes upwardlyand outwardly tothe top surface 30. 1

The flat screw-head 40 shown in Figure 6 is provided with a diametricalslot or recess 42- having" nearly parallel side walls and a flathorizontal bottom, with minimum width at the cen'e; -'tral portion. Theend walls of this recess slope upwardly and outwardly to reach the topsurface 40 slightly inward of the circumference of this surface. Tworadial recesses 44, having parallel 7 side walls, extend at right anglesto the recess 42. Each of the recesses 44 has a bottom surface whichslopes outwardly and downwardly and then upwardly to the top surface ofthe screwhead. p

In Figure 7 is illustrated a fillister screw-head having a slightlyconvex top surface 50 with a diametrical slot or recess 52 extendingacross the upper portion of the head and opening out on the cylindricaledge surface 54. The bottom of the slot 52 is horizontal and flat exceptfor the rend portions which slope downwardly and 52. Each of therecesses 58 is made" with parallel side walls and a bottom which slopesoutwardly and downwardly to the cylindrical edge surface 54 of thescrew-head. The lowermost points of the recesses 52 and 58 aresubstantially above the fiat horizontal shoulder underneath thescrew-head, the relation being similar to that in the rounded head shownin Figures 1, 2 and It is evident that various modifications and changesmay be made in .thespecific embodiments of the inventionherein shown andde- "scribed without departing fro'mfthe spirit or scope thereof asdeflned in the following claims.

outwardly-as atii." Tworadial recesses 58 are 7 arranged to extend atright anglesto the recess What I claim is: v p r 1. A screw-head havinga convex upper surface and an annular under surface, said head having adiametrical slotswith a bottom paifiel to but substantially above theplane of said surface, said head having a pair of radial slots at rightangles to said diametrical slot, each said" radial slot having a bottomwhich slopes out-- wardly and downwardly from substantially the;

uppermost point of said head to a point below" the level of the bottomof said diametrical 'slo t,-,-

2. A screw-head having a f'd iametrical' slot adapted to receive the endof a screwdrivensaid head also having a pair of radial slots at rightangles to said diametricalslot, the bottom ;of each radial slot slopingdownwardly andfloutwardly from approximately the top surface of the headto a point below thelevei of the bottom of said diametrical slot.

' GRANT J. HOLT.

